We have been using Basenje-Grayhound cross-breed dogs for two years as models in which to evaluate drug effects on pulmonary mechanics in experimental canine asthma. During these studies, it has become apparent that this particular breed of dog has unique features not seen in other animal models of asthma. These include: (1) changes in pulmonary resistance and compliance of the magnitude seen in human asthma during acute attacks, (2) hyperirritable airways characteristic of human asthmatic airways between attacks, (3) a major component of ascaris-induced bronchoconstriction not vagally mediated, and (4) progressive development of chronic reactive airway disease. These dogs appear to mimic the disease processes of asthma much more closely than previously described animal models, and thus provide a more realistic model to study the pathogenesis, pathophysiology and progression of asthmatic disease. In addition, they provide an ideal test situation for innovative therapeutic approaches. This model offers a unique opportunity to elucidate mechanisms responsible for the asthmatic state and to provide better methods of prevention and treatment of a common chronic disabling disease.